Structural panel

Abstract

A door or other structural panel of the type which has a pair of opposed, congruent sheets spaced apart by a frame to define a separation space between the sheets which may be filled with a core, such as foam. The edge of each sheet has a zig-zag portion which defines a ledge on the outer side of the sheet and a ridge on the inner side of the sheet. The frame member between the sheets at each edge has on each of two sides a projecting flange and a projecting hook which interlock with the zig-zag portion of the sheets to create a mechanical engagement between the sheets and the frame member. The flow of liquid foam into the separation space is controlled by a rib projecting inwardly from the sheet and by a resilient foam block slightly compressed between the sheets. Methods of manufacturing such panels are provided, including by sliding the beams onto the sheet edges and tapping the beams into a rigid state, and by employing temporary frame members which can be removed and re-used after the foam hardens.

We claim: 
     
       1. A structural panel comprising: (a) a pair of opposed, congruent sheets spaced apart by a frame which includes a beam located longitudinally along an edge of each of the sheets, each sheet having an outer side and an inner side facing the inner side of the other sheet, the sheets defining a separation space between them;   (b) wherein the edge of each of the sheets has an inwardly projecting zig-zag defining a ledge on the outer side of the sheet and a ridge on the inner side of the sheet;   (c) wherein along a longitudinal edge of the beam a flange extends from the beam, the flange having a connected leg which is an extension of said beam and is outward of said ledge and having a free leg overlying said ledge and, spaced apart from the flange, a hook projects from the beam into the separation space, the hook including a post projecting inwardly from the beam inward of said ledge and a cross member projecting outwardly from the post inward of said ridge toward the inner side of the sheet; and   (d) wherein the sheet and the beam are adapted so that the ledge fits closely between the flange and the hook thereby establishing a mechanical engagement which restrains movement between the edge and the beam in two mutually orthogonal directions.   
     
     
       2. A structural panel according to claim 1, further comprising: (e) a foam core in the separation space, the foam core being hardened foam which was introduced into the separation space in a liquid state; and   (f) a rib projecting inwardly from the inner side of at least one of the sheets so that the incoming liquid foam encounters a partial barrier which partially retards the flow of the liquid foam in a region of the separation space beyond the barrier beyond the barrier.   
     
     
       3. A structural panel according to claim 1, further comprising: (e) a foam core in the separation space, the foam core being hardened foam which was introduced into the separation space in a liquid state; and   (f) a resilient foam block located in the separation space and in contact with the inner sides of both sheets, thereby substantially blocking the flow of the liquid foam in the region of the block.   
     
     
       4. A structural panel comprising: (a) a pair of opposed, congruent sheets spaced apart by a frame which includes a beam located longitudinally along an edge of each of the sheets, each sheet having an inner side facing the inner side of the other sheet, the sheets defining a separation space between them;   (b) wherein from the edge of each of the sheets a flange and, spaced apart from the flange, a hook project inwardly, the hook including a post projecting from the sheet and a cross member projecting from the post toward the beam;   (c) wherein the beam has an inward side facing the separation space and an opposite outward and wherein along a longitudinal edge of the beam there is a zig-zag projecting into the separation space and defining a ledge on the outward side of the beam and a ridge on the inward side of the beam; and   (d) wherein the sheet and the beam are adapted so that the beam ledge fits closely between the sheet flange and the hook post, and the hook cross member embraces the beam ridge, thereby establishing a mechanical engagement between the sheet and the beam.   
     
     
       5. A method of manufacturing a structural panel, comprising the steps of: (a) providing a pair of congruent sheets, each sheet having an outer side, an inner side and a plurality of edges defining the shape of the sheet, at least one of the edges of each sheet having an inwardly projecting zig-zag which defines a ledge on the outer side of the sheet and a ridge on the inner side of the sheet;   (b) providing at least one beam having along each of two of its opposed longitudinal edges a projecting flange and, spaced apart from the flange, a projecting hook, the hook including a post projecting from the beam and a member projecting transversely from the post;   (c) holding the two sheets in opposed, parallel congruent relationship;   (d) slidably feeding the beam along the said at least one edge of each sheet so that each sheet ledge fits closely between a beam flange and a beam hook post and so that each sheet ridge is embraced by a beam hook, thereby mechanically engaging the sheet edges to the beam's opposed longitudinal edges, the beam forming a side of the panel; and   (e) providing other framing between the sheets along each sheet edge which is not attached by the steps (a) through (d).   
     
     
       6. A method of manufacturing a structural panel as in claim 5, comprising the further steps of: (f) providing each beam with mitered ends;   (g) applying the steps (a) through (d) to all of the edges of the sheets and slidably feeding each of the beams to the point at which each mitered end is immediately adjacent to another mitered end; and   (h) applying one or more short, light force impulses to one or more mitered ends until each mitered end is abutted tightly against another mitered end, thereby rendering the beams into a substantially rigid frame for the panel.   
     
     
       7. A method of manufacturing a structural panel, comprising the steps of: (a) providing a pair of substantially planar, congruent sheets, each sheet having an inner side and a plurality of edges defining the shape of the sheet and the number of panel edges;   (b) providing a plurality of permanent frame members;   (c) holding the two sheets in opposed, parallel congruent relationship;   (d) fastening each permanent frame member between an edge of each of the sheets, thereby making a partial peripheral frame which forms fewer than all of the edges of the panel;   (e) providing one or more removable frame members, their number being equal to the number of panel edges not framed pursuant to steps (a) through (d);   (e) temporarily fastening a removable frame member to each unframed panel edge, whereby the sheets, the permanent frame members and the temporary frame members form a separation space between the sheets;   (f) introducing foam into the separation space in a liquid state through a port in a sheet, a permanent frame member or a temporary frame member;   (g) allowing or hastening the foam to solidify into a foam core; and   (h) removing the temporary frame member or members.